1. Field of the Invention
The present invention relates to a lens driving device, and more particularly, to a lens driving device capable of performing zooming and automatic focusing using a single actuator.
2. Description of the Related Art
Optical devices such as cameras, camcorders, compact zoom cameras, security cameras, and micro-aircrafts have a structure for moving lenses to perform optical zooming.
In order to perform zooming, diverse structures for moving lenses have been developed, which usually adopt a cam driving mechanism. This cam driving mechanism includes a lens barrel rotated by an actuator such as an electromagnetic motor, and each lens is moved along a cam-shape slot on an outer circumference of the lens barrel so that the relative distance of the lenses is changed to perform zooming.
On the other hand, in the small camera modules for mobile communication terminals or Personal Digital Assistants (PDAs), zooming is performed only at predetermined zoom ratios.
FIGS. 1 and 2 illustrate a zooming method in which lenses are arranged at predetermined positions to perform zooming. In order to perform zooming as illustrated in FIGS. 1a and 2a, the relative distance of two lenses ML1 and ML2 is changed in general, and also additional fixed lenses FL1 and FL2 may be provided to enhance optical capability.
At this time, in order to perform zooming, the movable lenses ML1 and ML2 are moved from the initial positions P1 and P4 to the zoom positions corresponding to the set zoom ratios. For example, they are moved to P3 and P6 with a zoom ratio of 2 as shown in FIG. 1b, or to P2 and P5 with a zoom ratio of 2 and to P3 and P6 with a zoom ratio of 3. In order for such movement of the lenses, a guide slot as shown in FIGS. 1b and 2b is provided on an outer circumference of the lens barrel, which is rotated to move the lenses along the guide slot.
As described above, the movable lenses ML1 and ML2 are moved to the zoom positions corresponding to the predetermined zoom ratios, and then the relative distance between the movable lenses ML1 and ML2 is changed to perform zooming.
However, if only zooming is performed as described above, the focus distance of the object is not adjusted, and thus the optical characteristics are degraded, hindering achievement of high definition and high picture quality.
To solve such a problem, zooming and auto focusing is required, which requires so many mechanical apparatuses and control circuits, complicating the structure.
Especially, in order to perform optical zooming and auto focusing, two drivers are needed, which in turn, increases volume, weight and power consumption, making it difficult to apply to small camera modules required for mobile communication terminals or PDAs.